1. Field of the Invention
This invention relates to mobile transport equipment for handling drums and especially to apparatus adapted for use in association with fork lift trucks and the like for lifting and transporting multiple drums simultaneously.
2. Description of the Related Art
Various types of mobile carriers for handling multiple drums are known in the art and it is common practice to handle such drums while arranged in a symmetrical cluster. A clamping device is used to engage and latch onto the rim of each drum in the cluster and then the drums are lifted simultaneously and transported to a new location. This is generally accomplished with an apparatus adapted for use as an attachment for a forklift truck or the like.
Typical prior art apparatus of this type is described in Erickson U.S. Pat. No. 3,338,616, Lund and Erickson U.S. Pat. No. 3,718,228, and Berg U.S. Pat. No. 4,911,105.
U.S. Pat. No. 3,338,616 discloses a drum handling apparatus designed to handle four drums simultaneously. The drums are arranged in a symmetrical cluster about a central axis so that the cluster defines a four-pointed-star-shaped central space.
The apparatus includes a clamping device that carries four sets of jaws, each set being adapted to clamp onto the rim of one of the drums. The clamping device is positioned by a forklift truck or the like over the central space and then lowered into the space to a clamping position. The lowering and lifting movement of the device is effective to operate the jaws sequentially as needed throughout the drum handling cycle.
The clamping device is suspended below a horizontal mounting plate by means of four suspension bolts that extend downwardly through respective holes formed in the plate. The holes are considerably larger in diameter than the bolts and each bolt forms part of a bolt assembly that includes a relatively large diameter washer. The washers are located below the respective bolt heads and bear against the top surface of the mounting plate in the surface portions that surround the holes. Accordingly, the washers are able to slide against the top surface of the mounting plate to enable the suspension bolts (as well as the clamping device) to move horizontally in any direction within the limits defined by the edges of the bolt holes.
When sliding movement occurs, it is generally caused by engagement between the clamping device and the drums as the clamping device is lowered into the central space defined by the sides of the drums. This engagement urges the clamping device into approximate vertical alignment with the central axis of the four-drum cluster.
U.S. Pat. No. 3,718,228 discloses a drum handling apparatus similar to that of U.S. Pat. No. 3,338,616, but wherein the clamping device has a much longer vertical dimension. The apparatus has the capability of handling, during each lifting and transporting cycle, from one to four drums, as the situation requires. This capability is achieved by engaging and restraining each drum during the handling process in such a way as to prevent tipping. Without this feature an attempt to handle less than four drums would result in excessive tipping when the drum or drums are lifted.
More particularly, the clamping device is provided with relatively long vertical guide members that engage the sides of the drum or drums as low as the middle cylindrical panel (or central panel) as defined by the annular drum rings. These guide members are effective to prevent any excessive inward tipping of the bottom of the drum or drums as they are lifted regardless of the number of drums being handled (assuming four or less).
U.S. Pat. No. 4,911,605 discloses a multiple drum handling apparatus similar to that of U.S. Pat. No. 3,718,288, except that the clamping device has modified clamping jaws to better accommodate “L” shaped peripheral chime rings currently used on molded plastic drums.
Each of the prior art assemblies described above has a frame adapted to be carried by a forklift truck or the like. The forks of the lift truck are inserted in shoes (horizontal parallel tubular members) that form part of the frame.
The frame also has a pair of laterally spaced vertical legs located at the rearward end thereof adjacent the masts of the lift truck. The legs extend downwardly and (in the case of a four-drum cluster) provide back rests adapted to engage two of the drums of the cluster.
In the operation of the various multiple drum handling assemblies shown in the above patents, the apparatus is first carried by a forklift truck or the like to a preliminary position adjacent to the drum cluster. At this point, the latching device is urged to a centered position relative to the mounting plate by centering springs. In the case of a four-drum cluster, the operator of the lift truck moves the handling apparatus toward one side of the cluster until the back rests engage two of the drums. In this position, the latching device carried by the frame should be located over the central space and in approximate forward/rearward linear alignment with the central vertical axis of the drum cluster.
Also, the lift truck operator, by visual reference, locates the lift truck so as to position the clamping device in lateral (left/right) alignment with the central vertical axis of the cluster. This lateral positioning may be accomplished more accurately by the operator than the forward/rearward alignment due to his clearer view of the left/right position of the latching device.
Then, as the latching device is lowered into the central space, vertical guides associated with the latching device may engage portions of the drums as necessary to urge the latching device into more accurate vertical alignment with the central vertical axis of the drum cluster. This resulting movement, which may be in any horizontal direction, is enabled through the sliding movement of the suspension bolt assembly washers or the suspension plate, on the mounting plate.
One problem associated with drum handling apparatus of the type described is that the initial lateral location of the latching device relative to the frame could be at its left or right limit position rather than on the forward/rearward centerline of the frame. This could occur, for example, if the suspension bolt assemblies or suspension plate had slid sideways prior to initiation of the handling process.
If the fork-lift truck operator set the initial lateral position of the clamping device relative to the central vertical axis of the drum cluster while the clamping device was considerably right or left of center relative to the frame, poor load balance could result.
The drum handling apparatus of the present invention eliminates the problems described above and affords other features and advantages heretofore not obtainable.